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/*
* Copyright (c) 2000, 2001, 2002 Virtual Unlimited B.V.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
*/
/*!\file elgamal.h
* \brief ElGamal algorithm.
*
* For more information on this algorithm, see:
* "Handbook of Applied Cryptography",
* 11.5.2: "The ElGamal signature scheme", p. 454-459
*
* Two of the signature variants in Note 11.70 are implemented.
*
* \todo Implement ElGamal encryption and decryption.
*
* \todo Explore the possibility of using simultaneous multiple exponentiation,
* as described in HAC, 14.87 (iii).
*
* \author Bob Deblier <bob.deblier@pandora.be>
* \ingroup DL_m DL_elgamal_m
*/
#ifndef _ELGAMAL_H
#define _ELGAMAL_H
#include "mpbarrett.h"
#ifdef __cplusplus
extern "C" {
#endif
/**
* The raw ElGamal signing funcion, variant 1.
*
* Signing equations:
*
* \li \f$r=g^{k}\ \textrm{mod}\ p\f$
* \li \f$s=k^{-1}(h(m)-xr)\ \textrm{mod}\ (p-1)\f$
*
* @param p The prime.
* @param n The reducer mod (p-1).
* @param g The generator.
* @param rgc The pseudo-random generator.
* @param hm The hash to be signed.
* @param x The private key value.
* @param r The signature's \e r value.
* @param s The signature's \e r value.
* @retval 0 on success, -1 on failure.
*/
BEECRYPTAPI /*@unused@*/
int elgv1sign(const mpbarrett* p, const mpbarrett* n, const mpnumber* g, randomGeneratorContext* rgc, const mpnumber* hm, const mpnumber* x, mpnumber* r, mpnumber* s)
/*@modifies r, s */;
/**
* The raw ElGamal signing funcion, variant 3.
*
* Signing equations:
*
* \li \f$r=g^{k}\ \textrm{mod}\ p\f$
* \li \f$s=xr+kh(m)\ \textrm{mod}\ (p-1)\f$
*
* @param p The prime.
* @param n The reducer mod (p-1).
* @param g The generator.
* @param rgc The pseudo-random generator.
* @param hm The hash to be signed.
* @param x The private key value.
* @param r The signature's \e r value.
* @param s The signature's \e r value.
* @retval 0 on success, -1 on failure.
*/
BEECRYPTAPI /*@unused@*/
int elgv3sign(const mpbarrett* p, const mpbarrett* n, const mpnumber* g, randomGeneratorContext* rgc, const mpnumber* hm, const mpnumber* x, mpnumber* r, mpnumber* s)
/*@modifies r, s */;
/**
* The raw ElGamal verification funcion, variant 1.
*
* Verifying equations:
*
* \li Check \f$0<r<p\f$ and \f$0<s<(p-1)\f$
* \li \f$v_1=y^{r}r^{s}\ \textrm{mod}\ p\f$
* \li \f$v_2=g^{h(m)}\ \textrm{mod}\ p\f$
* \li Check \f$v_1=v_2\f$
*
* @warning The return type of this function should be a boolean, but since
* that type isn't as portable, an int is used.
*
* @param p The prime.
* @param n The reducer mod (p-1).
* @param g The generator.
* @param hm The hash to be signed.
* @param y The public key value.
* @param r The signature's \e r value.
* @param s The signature's \e r value.
* @retval 1 on success, 0 on failure.
*/
BEECRYPTAPI /*@unused@*/
int elgv1vrfy(const mpbarrett* p, const mpbarrett* n, const mpnumber* g, const mpnumber* hm, const mpnumber* y, const mpnumber* r, const mpnumber* s)
/*@*/;
/**
* The raw ElGamal verification funcion, variant 3.
*
* Verifying equations:
*
* \li Check \f$0<r<p\f$ and \f$0<s<(p-1)\f$
* \li \f$v_1=g^{s}\ \textrm{mod}\ p\f$
* \li \f$v_2=y^{r}r^{h(m)}\ \textrm{mod}\ p\f$
* \li Check \f$v_1=v_2\f$
*
* @warning The return type of this function should be a boolean, but since
* that type isn't as portable, an int is used.
*
* @param p The prime.
* @param n The reducer mod (p-1).
* @param g The generator.
* @param hm The hash to be signed.
* @param y The public key value.
* @param r The signature's \e r value.
* @param s The signature's \e r value.
* @retval 1 on success, 0 on failure.
*/
BEECRYPTAPI /*@unused@*/
int elgv3vrfy(const mpbarrett* p, const mpbarrett* n, const mpnumber* g, const mpnumber* hm, const mpnumber* y, const mpnumber* r, const mpnumber* s)
/*@*/;
#ifdef __cplusplus
}
#endif
#endif
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